Fabrication and Structural Characterization of Module-Assembled Amphiphilic Conetwork Gels

Structural analysis of inhomogeneity-free poly(ethylene glycol)-poly(dimethylsiloxane) (PEG PDMS) amphiphilic conetwork gels has been performed by the complementary use of small-angle X-ray and neutron scattering. Because of the hydrophobicity of PDMS units, the PEG-PDMS gels exhibit a microphase-separated structure in water. Depending on the volume fraction of; PDMS, the microphase-separated structure varies from core-shell to lamellar. The obtained X-ray and neutron scattering profiles are reproduced well using a core-shell model together with a Percus-Yevick structure factor when the volume fraction of PDMS is small. The domain size is much larger than the size of individual PEG and PDMS unit, and this is explained using the theory of block copolymers. Reflecting the homogeneous dispersion conditions in the as-prepared state, scattering peaks are observed even at a very low PDMS volume fraction (0.2%). When the volume fraction of PDMS is large, the microphase-separated structure is lamellar and is demonstrated to be kinetically controlled by nonequilibrium and topological effects.